Data communication systems comprise three components: a transmitter; a transmission channel; and a receiver. Transmitted data become altered due to noise corruption and channel distortion. To reduce the presence of errors caused by noise corruption and channel distortion, redundancy is intentionally introduced, and the receiver uses a decoder to make corrections. In modern data communication systems, the use of error correction codes plays a fundamental role in achieving transmission accuracy, as well as in increasing spectrum efficiency. Using error correction codes, the transmitter encodes the data by adding parity check information and sends the encoded data through the transmission channel to the receiver. The receiver uses the decoder to decode the received data and to make corrections using the added parity check information.
Stochastic computation was introduced in the 1960's as a method to design low precision digital circuits. Stochastic computation has been used, for example, in neural networks. The main feature of stochastic computation is that probabilities are represented as streams of digital bits which are manipulated using simple circuitry. Its simplicity has made it attractive for the implementation of error correcting decoders in which complexity and routing congestion are major problems, as disclosed, for example, in W. Gross, V. Gaudet, and A. Milner: “Stochastic implementation of LDPC decoders”, in the 39th Asilomar Conf. on Signals, Systems, and Computers, Pacific Grove, Calif., November 2005.
A major difficulty observed in stochastic decoding is the sensitivity to the level of switching activity—bit transition—for proper decoding operation, i.e. switching events become too rare and a group of nodes become locked into one state. To overcome this “latching” problem, Noise Dependent Scaling (NDS), Edge Memories (EMs), and Internal Memories (IMs) have been implemented to re-randomize and/or de-correlate the stochastic signal data streams as disclosed, for example, in US Patent Application 20080077839 and U.S. patent application Ser. No. 12/153,749 (not yet published).
It would be desirable to provide methods and systems for improving performance of iterative signal processing such as, for example, stochastic decoding.